1. Field of the Invention
This invention relates generally to long distance carriers, Internet Service Providers (ISPs), and information content delivery services/providers and long distance carriers. More particularly, it relates to emergency call systems (e.g., E9-1-1) including wireless and Internet Protocol (IP) based Voice Over Internet Protocol (VoIP) emergency call systems.
2. Background of Related Art
9-1-1 is a phone number widely recognized in North America as an emergency phone number that is used to contact emergency dispatch personnel. Enhanced 9-1-1 (E9-1-1) is defined by an emergency call being selectively routed to an appropriate PSAP, based on a special identifier (P-ANI, or “Pseudo Automatic Number Identifier”, also referred to as “ESxK”), and includes the transmission of callback number and location information when 9-1-1 is used. E9-1-1 may be implemented for landline, cellular or VoIP networks. Regardless of the network type, a 9-1-1 service becomes E-9-1-1 when automatic number identification and automatic location information related to the call is provided to the 9-1-1 operator at the PSAP.
A Public Safety Answering Point (PSAP) is a dispatch office that receives 9-1-1 calls from the public. A PSAP may be a local, fire or police department, an ambulance service or a regional office covering all services. As used herein, the term “PSAP” refers to either a PSAP, or to an Emergency Call Center (ECC), a VoIP term.
Distributed Emergency Call Systems in Telecommunications are in general very complex computing systems. Emergency Calls that originate from a VoIP network use well proven routing paradigms already used for Cellular 911 calls, or for traditional Landline 911 calls. These paradigms usually work well, because VoIP customers can usually be grouped into two categories, a mobile one that resembles a cellular user and a stationary one resembling landline usage.
Traditional Landline paradigms provide the most accurate location, but require the subscriber's address to be provisioned into a Landline ALI (Automatic Location Identifier). This pre-provisioning (often referred to as SOI “Service Order Interface” loading) usually takes a few days between the caller notifying their service provider of their address change, and this change being reflected in the Landline ALI. During this window a 911 call will be routed using the “old” data still in the Landline ALI. The fastest possible landline ALI provisioning takes at least several hours.
Landline systems use pre-provisioned Subscriber addresses, where the Landline ALI provisioning process (i.e. SOI) insures a match to an MSAG record, which contains an ESN used to route Emergency Calls to a PSAP.
Cellular systems either use triangulation technologies to find a latitude & longitude of the caller, then use modern GIS systems to query for the PSAP polygon that contains this location. These polygons can lead to a different, neighboring PSAP than an equivalent address provisioned in a Landline ALI, but this discrepancy is accepted by PSAPs because the location itself is likely to be imprecise due to measurement errors—sometimes the location is off by hundreds of feet.
VoIP systems use proprietary technologies, usually based on GIS polygons, or based on provisioning the caller in the traditional Landline ALI which takes at least a few hours, and sometimes as long as a few days.
A significant disadvantage of the conventional technology is that non-mobile VoIP callers who know their street address must choose between (1) their ability to dial 911 immediately, but with the chance that calls will be routed to a neighboring PSAP, possibly delaying responders; and (2) waiting a few hours (up to days), during which their calls will route to the previous PSAP. But after this delay, the call will route to the same PSAP as a traditional landline 911 call.